Energy absorbing elements, often called crash boxes, which connect the longitudinal and cross members of a motor vehicle frame are known from various sources. DE 197 51 513 A1 describes a crash box obtained from a rectangular, longitudinally welded aluminum tube by means of cutting slots into the ends of the tube, and the tongues thus obtained being bent over to obtain contact surfaces for large-area support of the crash box on a member of the frame. This technique is essentially specified for tubes with a rectangular cross-section because the greater the number of corners of the tubular cross-section, the greater the number of slots which must be cut to be able to bend the tongues, and their required bending processes. Moreover, for non-rectangular cross-sections, the problem may result that the bent tongues cannot be readily placed on the member on which they are to rest in support.
From DE 201 21 532 U1, an energy absorbing element is known in which a tube section of aluminum or steel of a rectangular cross-section is filled with polyurethane foam to stiffen it. Although reference is made to the low weight of the polyurethane foam, it is evident that any stiffening of the energy absorbing element realized through its use will inevitably also result in weight and cost increases.